Additives for perfluoropolyether oils

ABSTRACT

Use as stabilizers of perfluoropolyether oils at high temperatures, higher than 200° C., of compounds not containing phosphor and having the general formula (A):

The present invention relates to the use of fluorinated compounds asstabilizing additives of perfluoropolyether oils for their use at hightemperatures.

More specifically the present invention relates to the use offluorinated compounds as stabilizing additives of perfluoropolyetheroils for their use at high temperatures, in oxidizing environment and inthe presence of metals.

It is known that perfluoropolyether fluids are lubricating oils usedalso at high temperatures. However, said fluids show the drawback thatin oxidizing environment (for example oxygen, air) and in the presenceof metals they have a limited thermal stability.

It is also known in the prior art that said drawback can be reduced byadding to perfluoropolyether fluids stabilizing additives. Saidstabilizing additives are generally phosphor compounds whereinsubstituents of perfluoroalkyl, perfluorooxyalkyl and aromatic type arepresent. The synthesis of said compounds is generally complex or usesreactants at a high cost. The following patents can for example bementioned. U.S. Pat. No. 4,681,693 describes stabilizers forperfluoropoly-ether fluids having a structure formed by arylphosphines,or derivatives thereof, linked to PFPE radicals through one oxygen orsulphur atom. Said compounds are synthesized by a more step processwhich includes intermediates difficult to be prepared. EP 597,369describes stabilizers for perfluoropolyether fluids based on substitutedphosphazene derivatives, where on the phosphazene ring both aromatic and(per)fluoropolyether radicals are contemporaneously present. Thesynthesis of said additives requires a double substitution on thephosphazene ring. Besides the starting phosphazene product has a highcost. This represents a further drawback from the industrial point ofview.

U.S. Pat. No. 5,326,910 describes perfluoropolyether phosphotriazinederivatives as stabilizers for perfluoropolyether oils. Said derivativesare synthesized with several steps, using reactants of difficultpreparation, such for example perfluorinated epoxides.

U.S. Pat. No. 5,550,277 describes stabilizers for perfluoropolyetherfluids based on aromatic phosphates or phosphonates substituted byperfluoropolyether groups. The synthesis process is very complicated, itrequires more steps and furthermore it employes the use ofmetallo-organic reactants, such for example butyl lithium, which are ofdifficult industrial use for the problems related to the plant safety.

Patent application WO 99/51,612 describes new phosphoric esters, inparticular substituted arylphosphates, where at least one of thesubstituents is a radical of perfluoropolyether type.

In the preparation method of said additives, aromatic phosphoricchloroesters, having a high cost, are used. As described in the Examplesof the patent application, said esters are obtained by reacting aromaticalcohols with POCl₃, which is a toxic and scalding substance, requiringspecific equipments for the use in an industrial scale.

According to the prior art the substances used as stabilizing additivesfor perfluoropolyether oils contain phosphor and are obtained by using,as seen, synthesis processes comprising various steps or, alternatively,using expensive reactants.

The Applicant has surprisingly found additives which even not containingphosphor in the molecule can be suitably used as perfluoropolyether oilstabilizers at high temperatures, even in oxidizing environment and inthe presence of metals. Furthermore said additives can be obtained withsimplified synthesis methods using cheap reactants.

An object of the present invention is the use as stabilizers ofperfluoropolyether lubricating oils at high temperatures, higher than200° C., of compounds having the following general formula (A):

wherein:

-   -   X, Y, X′, Y′, equal or different, are independently the one from        the other H; NO₂; C₁–C₄ alkyl; C₁–C₄ alkoxy, preferably methoxy        group;    -   Z=—CH₂—; >C═O (carbonyl);    -   m and n are integers such that m is in the range 0–80, extremes        included; n is in the range 0–20, extremes included; m+n being        >1;        the molecular weight of the perfluoropolyether part (units with        indexes m and n respectively) being from 500 to 10,000,        preferably from 1,000 to 4,000.

Also mixtures of one or more formula (A) additives can be used.

Preferably the general formula (A) products are selected from thefollowing:

wherein m is in the range 0–80, extremes included; n is in the range0–20, extremes included, m/n preferably being from 0.5 to 4 when n isdifferent from zero and m+n is such to give the above molecular weight.

The general formula (A) compounds can be prepared according to U.S. Pat.No. 3,810,874, EP 165,649, EP 165,650, U.S. Pat. No. 3,250,807. They aregeneally obtainable in a single step by a reaction between aperfluoropolyether derivative of formula:HOZCF₂(OCF₂CF₂)m(OCF₂)nOCF₂ZOH  (B)wherein Z, m and n are as above, with a suitable aromatic reactanthaving the substituents X, Y, X′ and Y′ as defined in formula (A). Forexample a nucleophilic substitution or esterification reaction can beused. In the former case the alcoholate of compound (B) (Z=—CH₂—), isused, in the latter case compound (B) with Z=>C═O. See the abovepatents.

The formula (A) compounds of the present invention are used asstabilizers for perfluoropolyether oils, available on the market as forexample FOMBLIN®, marketed by Ausimont.

Said oils have perfluoroalkyl end groups, are liquid with a very lowvapour pressure value and have a viscosity at 20° C. generally in therange 10–100,000 cSt, preferably 30–2,000 cSt.

The perfluoropolyether oils are formed by repeating units statisticallydistributed along the chain, and have for example the followingstructures:B—O—[C₃F₆O]_(m′)(CFT′O)_(n′)—B′  (1)wherein:

-   -   T′=F, CF₃;    -   B and B′, equal to or different from each other, are selected        from —CF₃, —C₂F₅ or —C₃F₇;    -   m′ and n′ are integers such that the m′/n′ ratio is in the range        20–1,000, n′ being different from zero, and the product        viscosity is within the above limits;    -   said products can be obtained by photooxidation of the        perfluoropropene as described in GB 1,104,432, and by subsequent        conversion of the end groups as described in GB 1,226,566.        C₃F₇O—[C₃F₆O]_(o′)-D  (2)        wherein:    -   D is equal to —C₂F₅ or —C₃F₇;    -   o′ is an integer such that the product viscosity is in the above        range;    -   said products can be prepared by ionic oligomerization of the        perfluoropropylenoxide and subsequent treatment with fluorine as        described in U.S. Pat. No. 3,242,218.        B—O—[CF(CF₃)CF₂O]_(q′)(C₂F₄O)_(r′)(CFT′O)_(s′)—B′  (3)        wherein:    -   T′ is as above;    -   B and B′, equal to or different from each other, are selected        from —CF₃, —C₂F₅ or —C₃F₇;    -   q′, r′ and s′ are integers and can have also the value of zero,        with the proviso that they are not all contemporaneously equal        to zero, and are such that the product viscosity is in the above        range, i.e. 10–100,000 sSt, preferably 30–2,000 cSt;    -   said products are obtainable a mixture photooxidation of C₃F₆        and C₂F₄ and subsequent treatment with fluorine as described in        U.S. Pat. No. 3,665,041.        B—O—(C₂F₄O)_(t′)(CF₂O)_(u′)—B′  (4)        wherein:    -   B and B′, equal to or different from each other, are selected        from —CF₃, —C₂F₅ or —C₃F₇;    -   t′ and u′ are integers such that the t′/u′ ratio is in the range        0.1–5, preferably 0.5–4, u′ being different from zero, and the        product viscosity is in the above range;    -   said products are obtained by photooxidation of C₂F₄ as reported        in U.S. Pat. No. 3,715,378 and subsequent treatment with        fluorine as described in U.S. Pat. No. 3,665,041.        B—O—(CF₂CF₂CF₂O)_(v′)—B′  (5)        wherein:    -   B and B′, equal to or different from each other, are selected        from —CF₃, —C₂F₅ or —C₃F₇;    -   v′ is a number such that the product viscosity is in the above        range;    -   said products are obtained as reported in EP 148,482.        D-O—(CF₂CF₂O)_(z′)-D′  (6)        wherein:    -   D and D′, equal to or different from each other, are selected        between —C₂F₅ or —C₃F₇;    -   z′ is an integer such that the product viscosity is in the above        range;    -   said products can be obtained as reported in U.S. Pat. No.        4,523,039.

The —C₃F₆O— unit in the above formulas can have structure —CF(CF₃)CF₂O—or —CF₂CF(CF₃)O—.

According to the present invention the class (4) perfluoropolyethers arepreferably used.

The formula (A) compounds are mixed with perfluoropolyether oils in apercentage from 0.01 to 10% by weight, preferably from 0.2 to 5% withrespect to the perfluoropolyether oil weight. Preferably the formula (I)compound is used.

To the aforesaid mixtures other additives commonly used in theperfluoropolyether lubricating compositions can be added.

The compositions comprising the invention additives can be used in thepresence of metals and in the presence of air and oxygen at hightempertures, higher than 200° C., up to the oil decompositiontemperature. In particular the invention additive can be used attemperatures of about 320° C., preferably up to 300° C.

The invention compositions, perfluoropolyether lubricating oil+additive,can be used for the above uses, preferably the additive has formula (I).

The following Examples are given for illustrative and not limitativepurposes of the invention.

EXAMPLES

Microoxidation Test

The microoxidation test used in the Examples has been carried out usingthe equipment described in the following publication: Carl E. Snyder,Jr. and Ronald E. Dolle, Jr., ASLE Transactions, 13(3), 171–180 (1975).The used operating conditions have been the following:

-   Perfluoropolyether oil utilized: Fomblin®M30 having kinematic    viscosity at 20° C. of 270 cSt (2.7·10⁸ m²/s) and acidity,    determined with the method indicated hereinafter, lower than 0.01 mg    KOH/g;-   Test temperature: 300° C.;-   Test duration: 24 h;-   Air flow: 1 litre/h;-   Metals dipped in the fluid: stainless steel (AISI 304) and titanium    alloy containing Al 6%, V 4% (Titanium 6A14V).

The tested fluid is introduced into the glass test tube of theequipment, shown in FIG. 1 of the above reference, and the test tubecharged with the fluid and the metal is weighed and brought to the testtemperature. The established time elapsed, the glass test tube is cooledto room temperature and weighed again. The per cent weight loss of thetested fluid is determined by the difference of the weight before andafter the thermal treatment. The fluid is then recovered and thekinematic viscosity and the acidity are determined. After the test thesurface aspect of the metals which have been dipped in the tested fluidis visually evaluated.

Determination of the Perfluoropolyether Oil Acidity Number

The acidity number of the tested PFPE is measured by mixing under alight nitrogen flow, in the order, 5 ml of KOH 0,01 N, 10 g of sample tobe tested, 30 ml of Freon 113 and 40 ml of MeOH. The base excess istitred with HCl 0.01 N by a potentiographic automatic titrator.

The acidity number N, is determined by the following formula:N=0.56·(B−A)/W,wherein B=ml of HCl 0.01 N used for the control test (without sample),A=ml of HCl 0.01 N used in the titration of the base excess and W is thesample weight in grams. Therefore N is expressed in mg KOH/g fluid.Determination of the Kinematic Viscosity of the Perfluoropolyether Oil

The kinematic viscosity has been determined by capillary viscosimeterCannon-Fenske according to the ASTM D 445 method.

Example 1

Synthesis of the bis(2,4-dinitro phenil) (per)fluoropolyether Derivative

11.8 g of potassium terbutylate are dissolved in 200 ml of terbutanol ina 500 ml three necked flask, equipped with mechanical stirrer, waterrefrigerant, thermometer and nitrogen head. Subsequently, maintainingthe reactor at room temperature by means of a water bath, 100 g of ZDOL®2000 of formula HOCH2CF₂(OCF₂CF₂)m(OCF2)nOCF₂CH₂OH MW=1966 EW=993,m/n=1.2 are dripped. When dripping is over, the reaction mixture is leftunder stirring for two hours under nitrogen head.

Lastly a solution composed of 21.2 g of 2,4-dinitro chlorobenzenedissolved in 28 ml of dioxane is slowly dripped at room temperature. Ayellow brownish precipitate mainly consisting of KCl immediately forms.

The reactor is left under stirring for one hour at room temperature,then for one hour at 65° C. and lastly for another hour at 75° C. Thereaction raw product is discharged in 600 ml of water. A turbid yellowbrownish oil separates and the aqueous supernatant is extracted with twoportions of 20 ml each of CF₂Cl—CFCl₂ having boiling point of 47.6° C.

The fluorinated phases are joined to the oil and the mixture isdecoloured by mixing with active carbon. The mixture is filtered onporous septum and dried, it is washed with two portions of 10 ml each ofethanol to remove the unreacted 2,4-dinitrochlorobenzene, it is driedunder vacuum at 60° C. for one hour. 92 g of product are isolated.

Characterization of the Product:

NMR ¹⁹F spectrum in ppm (with respect to CFCl₃=0): −51/−56 (17F,(OCF₂)_(n)); −87/−91 (42F, (OCF₂CF₂)_(m)); −76/−80 (4F, OCF₂CH₂O); NMR¹H spectrum in ppm (with respect to TMS): 5.1 (4H, OCF₂CH₂); 8.8 (2Haromatic CNO₂—CH—CNO₂); 8.6 (2H aromatic CNO₂ CH—CH—); 7.8 (2H aromaticRf-CH₂OC—CH—CH—); IR spectrum (cm⁻¹) intensity: (w)=weak, (m)=mean,(s)=strong, (vs)=very strong 3092(w), 1612(w), 1542(w), 1351(m),1207(vs), 1096(vs). Said NMR peakds show that the product has formula(I) for 91% by weight. NMR ¹⁹F spectrum in ppm (with respect to theCFCl₃=0): −81/−82 (0-CF ₂—CH₂—OH); NMR ¹H spectrum in ppm (with respectto the TMS): 4.0 (0-CF₂—CH ₂—OH).

Example 2

Synthesis of the bis(p-nitrophenyl) (per)fluoropolyether Derivative

In a flask, equal to that used in Example 1, potassium terbutylate,terbutanol and ZDOL® 2000 are added under the same conditions andamounts described therein.

Lastly a solution composed of 14.8 q of p-nitrofluorobenzene dissolvedin 30 ml of dioxane is slowly dripped at room temperature. The reactoris left under stirring for one hour at room temperature, then for onehour at 65° C. and lastly for two hours at 85° C. The reaction rawproduct is discharged in 600 ml of water. The oil is recovered asdescribed in Example 1. The dried reaction raw product is then washedwith two portions of 10 ml each of ethanol to remove the unreactedp-nitrofluorobenzene; it is dried under vacuum at 60° C. for one hour.85 g of product are isolated.

Characterization of the Product:

NMR ¹⁹F spectrum in p.p.m. (with respect to the CFCl₃=0): −51/−56 (17F,(OCF₂)_(n)); −87/−91 (42F, (OCF₂CF₂)_(m)); −76/−80 (4F, OCF₂CH₂O); NMR¹H spectrum in ppm (with respect to TMS): 4.8 (4H, OCF₂CH₂); 7.3 (4Haromatic in meta to NO₂); 8.3 (4H aromatic in ortho to NO₂); IR spectrum(cm⁻¹) intensity: (w)=weak, (m)=mean, (s)=strong, (vs)=very strong3090(w), 1789(w), 1596(m), 1596(m), 1522(m), 1456(w), 1350(s), 1200(vs),1100(vs). Said NMR peaks show that the product has formula (II) for 93%by weight. NMR ¹⁹F spectrum in ppm (with respect to CFCl₃=0): −81/−82(0-CF ₂—CH₂—OH). NMR ¹H spectrum in ppm (with respect to TMS): 4.0(0-CF₂—CH ₂—OH).

Example 3

Synthesis of the (per)fluoropolyether phenyl ester Having Formula

In a flask equal to that described in Example 1, 24 g of phenol, 200 gof an acylfluoride of formula:FOC(O)CF₂(OCF₂CF₂)m(OCF₂)nOCF₂C(O)Fprepared according to U.S. Pat. No. 3,715,378, having molecular weight2,400, m/n=1.3 and 30 g of NaF, are introduced, in the order. Theheterogeneous mixture is heated under stirring at 80° C. for two hours.When heating is over, the product is filtered and heated at 135° C. in avacuum of 0.5 mm Hg (67 Pa) to remove the unreacted phenol. 198 g of thedesired product are isolated.Characterization of the Product:

NMR ¹⁹F spectrum in p.p.m. (with respect to CFCl₃=0): −51/−56 (20F,(OCF₂)_(n)); −87/−91 (52F, (OCF₂CF₂)_(m)); −80/−84 (4F, OCF₂(O)O); NMR¹H spectrum in ppm (with respect to TMS): 7.5/7.3 (4H ortho); 7.3/7.2(6H: 2H in para, 4H in meta); IR spectrum (cm⁻¹) intensity: (w)=weak,(m)=mean, (s)=strong, (vs)=very strong 3588(w), 2364(w), 1805(vs),1593(m), 1494(s), 1204(vs).

Said NMR peaks show that the product has formula (I) for 100% by weight.

Example 4

Microoxidation Test of a perfluoropolyether Oil Added to the ProductObtained in Example 1.

50 g of perfluoropolyether oil Fomblin®M30 are added with 0.5 g of theproduct obtained in Example 1 (1% by weight of the additive with respectto the oil) and then introduced into the glass test tube for themicrooxidation test as above described. During the test the fluid hasmaintained limpid and no smoke development has been observed.

At the test end under the mentioned operating conditions a per cent lossΔP% of fluid equal to 1.6% by weight has been measured. The kinematicviscosity has substantially remained unchanged (Δη=+0.84%).

The fluid acidity has not changed. The metals recovered, from the fluidat the test end (stainless steel and Ti, Al, V alloy) did not showoxidation/corrosion signs, and their surface aspect was comparable withthat of the specimens of the same metals not subjected to the treatment.

Example 5

Microoxidation Test of a Perfluoropolyether Oil Added with the ProductObtained in Example 2.

Example 4 is repeated by using as additive 0.5 g of the product obtainedin Example 2.

At the test end under the mentioned operating conditions a per cent lossΔP% of fluid of 1.3% has been measured. The kinematic viscosity hassubstantially remained unchanged (Δη=+0.6%). The fluid acidity is notchanged. The metals recovered from the fluid at the test end (stainlesssteel and Ti, Al, V alloy) did not show oxidation/corrosion signs, andtheir surface aspect was comparable with that of the specimens of thesame metals not subjected to the treatment.

Example 6

Microoxidation Test of a Perfluoropolyether Oil Added with the ProductObtained in Example 3.

Example 4 is repeated by using as additive 0.5 g of the product obtainedin Example 3. At the test end under the mentioned operating conditions aper cent loss ΔP% of fluid equal to 1.7% and a kinematic viscosityvariation equal to Δη=+2.1% have been measured.

The fluid acidity is not changed. The metals recovered from the fluid atthe test end (stainless steel and Ti, Al, V alloy) did not showoxidation/corrosion signs, and their surface aspect was comparable withthat of the specimens of the same metals not subjected to the treatment.

Example 7 (Comparative)

Microoxidation Test of a Not Additivated Perfluoropolyether Oil inAbsence of Metals.

Example 4 is repeated without adding the additives of the presentinvention and in absence of metals in the perfluoropolyether oil.

During the test the development of white smokes has been observed.

At the test end under the mentioned operating conditions a per cent lossΔP% of fluid of 4.6% by weight and a kinematic viscosity variation equalto Δη=+0.5% have been measured. The measured final fluid acidity hasbeen 0.07 mg KOH/g.

Example 8 (Comparative)

Microoxidation Test of a Not Additivated Perfluoropolyether Oil in thePresence of Metals.

Example 4 is repeated without adding the additives of the presentinvention.

During the test the intense development of white smokes has beenobserved.

At the test end under the mentioned operating conditions a very high percent loss ΔP% of fluid equal to 82.8% by weight has been measured.

The measured final fluid acidity has been of 5.5 mg KOH/g. The surfaceaspect of the metals has resulted modified for the presence of evidentoxidation signs (browning).

Example 9

Microoxidation Test of a Perfluoropolyether Oil Added with the ProductObtained in Example 1.

Example 4 has been repeated but by using 0.125 g of the product obtainedin Example 1 (0.25% by weight of the additive with respect to the oil).

During the test the fluid has maintained limpid and no smoke developmenthas been observed.

At the test end under the mentioned operating conditions a per cent lossΔP% of fluid of 0.18% has been measured, while the kinematic viscosityhas substantially remained unchanged (Δη=+1.33%).

The fluid acidity is not changed. The metals recovered from the fluid atthe test end (stainless steel and Ti. Al, V alloy) did not showoxidation/corrosion signs, and their surface aspect was comparable withthat of the specimens of the same metals not subjected to the treatment.

The following Table 1 summarizes the results obtained in Examples 4–9.

TABLE 1 Final fluid after microoxidation test Concentration FluidKinematic Metal and used compounds weight viscosity Acidity treat- offormula (A) variation variation mg Ex. ment % by weight formula ΔP % Δη% KOH/g 4 Yes 1 (I) −1.6 0.84 <0.01 5 Yes 1 (II) −1.3 0.60 <0.01 6 Yes 1(III) −1.7 2.1  <0.01 7 No — — −4.6 0.5  0.07 comp 8 Yes — — −82.8 — 5.5comp 9 Yes 0.25 (I) −0.2 1.33 <0.01

1. A process for stabilizing perfluoropolyether lubricating oils at hightempertures, higher than 200° C., by mixing with said perfluoropolyetheroils compounds having the following general formula (A):

wherein: X, Y, X′, Y′, equal to or different, are independently the onefrom the other H; NO₂; C₁–C₄ alkyl; C₁–C₄ alkoxy, or methoxy group;Z=—CH₂—; >C═O carbonyl; m and n are integers such that m is in the range0–80, extremes included; n is in the range 0–20, extremes included, m+nbeing >1; the molecular weight of the perfluoropolyether part, unitswith indexes m and n, being from 500 to 10,000, wherein the compounds offormula (A) are mixed with the perfluoropolyether oils in a percentagefrom 0.2 to 5% by weight with respect to the perfluoropolyether oilsweight.
 2. The process of claim 1, wherein the general formula (A)compounds are selected from the following:

wherein m is in the range 0–80, extremes included; n is in the range0–20, extremes included, and m+n is such to give the above molecularweight.
 3. The process of claim 1, wherein the perfluoropolyether oilshave perfluoroalkyl end groups and have a viscosity at 20° C. in therange 10–100,000 cSt.
 4. The process of claim 1, wherein theperfluoropolyether oils have the repeating units statisticallydistributed along the chain and have the following structures:B—O—[C₃F₆O]_(m′)(CFT′O)_(n′)—B′  (1) wherein: T′=F, CF₃; B and B′, equalto or different from each other, are selected from —CF₃, —C₂F₅ or —C₃F₇;m′ and n′ are integers such that the m′/n′ ratio is in the range20–1,000, n′ being different from zero, and the product viscosity is inthe above limits;C₃F₇O—[C₃F₆O]_(o′)-D  (2) wherein: D is equal to —C₂F₅ or —C₃F₇; o′ isan integer such that the product viscosity is in the above range;B—O—[CF(CF₃)CF₂O]_(q′)(C₂F₄O)_(r′)(CFT′O)_(s′)—B′  (3) wherein: T′ is asabove; B and B′, equal to or different from each other, are selectedfrom —CF₃, —C₂F₅ or —C₃F₇; q′, r′ and s′ are integers and can take alsothe value of zero, with the proviso that they are not allcontemporaneously equal to zero, and are such that the product viscosityis in the above range;B—O—(C₂F₄O)_(t′)(CF₂O)_(u′)—B′  (4) wherein: B and B′, equal to ordifferent from each other, are selected from —CF₃, —C₂F₅ or —C₃F₇; t′and u′ are integers such that the t′/u′ ratio is in the range 0.1–5, u′being different from zero, and the product viscosity is in the aboverange;B—O—(CF₂CF₂CF₂O)_(v′)—B′  (5) wherein: B and B′, equal to or differentfrom each other, are selected from —CF₃, —C₂F₅ or —C₃F₇; v′ is a numbersuch that the product viscosity is in the above range;D-O—(CF₂CF₂O)_(z′)-D′  (6) wherein: D and D′, equal to or different fromeach other, are selected between —C₂F₅ or —C₃F₇; z′ is an integer suchthat the product viscosity is in the above range, wherein the —C₃F₆O—unit in the above formulas can have the structure —CF(CF₃)CF₂O— or—CF₂CF(CF₃)O—.
 5. The process of claim 1, wherein the perfluoropolyetheroils have structure (4).
 6. The process of claim 2, wherein the formula(I) compound is uesd.
 7. The process of claim 1, wherein in the mixingprocess other additives commonly used in perfluoropolyether lubricatingcompositions can be added.
 8. The process of claim 1, wherein thecompositions are used in the presence of metals and in the presence ofair and oxygen at high temperatures, higher than 200° C., up to the oildecomposition temperature.
 9. Compositions prepared by the process ofclaim
 1. 10. Compositions prepared by the process of claim 2, whereinthe additive has formula (I).
 11. The process of claim 1, wherein saidmolecular weight of the perfluoropolyether part is from 1,000, to 4,000.12. The process of claim 2, wherein m/n is from 0.5 to 4 when n isdifferent from zero.
 13. The process of claim 3, wherein said viscosityat 20° C. is in the range 30–2,000 cSt.
 14. The process of claim 4,wherein said t′/u′ ratio is in the range 0.5–4.
 15. The process of claim8, wherein said high temperatures are up to about 320° C.
 16. Theprocess of claim 8, wherein said high temperatures are up to 300° C.